requirements.txt updated to python 3.4

Author: arunsureshkumar

requirements.txt

@@ -11,7 +11,7 @@ mongomock==3.22.0
 pymongo==3.11.2
 pytest==4.6.11; python_version <= '3.5'
 pytest==6.2.1; python_version > '3.5'
-pytest-cov==2.8.1; python_version == '3.5'
+pytest-cov==2.8.1; python_version == '3.5' or python_version == '3.4'
 pytest-cov==2.10.1; python_version < '3.5' or python_version > '3.5'
 singledispatch==3.4.0.3
 # https://stackoverflow.com/a/58189684/9041712